Method for manufacturing a fibrous web

The invention relates to a Method for manufacturing a fibrous web， such as web of paper， board， tissue or the like. The method comprises forming an aqueous fibre suspension comprising cellulosic fibres from one or more raw material flows， and applying at least one chemical and/or physical control measure to the aqueous fibre suspension or at least one of its raw material flows for control of microbial activity in the aqueous fibre suspension or the raw material flow before an inlet of an intermediate residence entity， such as storage tower or broke tower， which has a delay time of at least one hour， preferably at least two hours. In this manner a starting ORP value for the aqueous fibre suspension is obtained. A final ORP value for the aqueous fibre suspension after an outlet of the said intermediate residence entity but before the formation of the fibrous web is measured， and maintained on a target level where the difference between the starting and final ORP values is less than 100 mV， optionally by adjusting the applied chemical and/or physical control measure(s). The aqueous fibre suspension is formed into a fibrous web and drying the fibrous web.